PID - Photoionization Detector Introduction The reason to...

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Photoionization Detector Introduction The reason to use more than one kind of detector for gas chromatography is to achieve selective and/or highly sensitive detection of specific compounds encountered in par- ticular chromatographic analyses. The selective determination of aromatic hydrocar- bons or organo-heteroatom species is the job of the photoionization detector (PID). This device uses ultraviolet light as a means of ionizing an analyte exiting from a GC column. The ions produced by this process are collected by electrodes. The current generated is therefore a measure of the analyte concentration. Theory If the energy of an incoming photon is high enough (and the molecule is quantum mechanically “allowed” to absorb the photon) photo-excitation can occur to such an extent that an electron is completely removed from its molecular orbital, i.e. ionization. A photoionization reaction: If the amount of ionization is reproducible for a given compound, pressure, and light source then the current collected at the PID’s reaction cell electrodes is reproducibly
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PID - Photoionization Detector Introduction The reason to...

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